[css-sizing] Fix copy-paste error

Author: fantasai

css-sizing/Overview.bs

@@ -146,7 +146,7 @@ Auto Box Sizes</h3>
 				and the “maximum cell width” in <a href="http://www.w3.org/TR/CSS21/tables.html#auto-table-layout">CSS2.1§17.5.2.2</a>.
 
 			: <dfn>max-content block size</dfn>
-			:: The box's “ideal” <a>size</a> in the <a>inline axis</a>.
+			:: The box's “ideal” <a>size</a> in the <a>block axis</a>.
 				Usually the <a>block size</a> of the content after layout.
 
 		: <dfn>min-content size</dfn>